THE EOCENE PERIOD. 299 
which distinguish their living representatives. At the same 
time, there are some amongst the Eocene quadrupeds which 
have a “ generalised” character, and which may be regarded 
as structural types standing midway between groups now 
sharply separated from one another. 
The order of the JZarsupia/s—including the existing Kan- 
garoos, Wombats, Opossums, Phalangers, &c.— is poorly 
represented in deposits of Eocene age. ‘The most celebrated 
example of this group is the Dvzdelphys gypsorum of the 
Gypseous beds of Montmartre, near Paris, an Opossum very 
nearly allied to the living Opossums of North and South 
America. 
No member of the Ldentates (Sloths, Ant-eaters, and Arma- 
dillos) has hitherto been detected in any Eocene deposit. 
The aquatic order of the Szvenians (Dugongs and Manatees), 
with their fish-like bodies and tails, paddle- shaped fore- 
limbs, and wholly deficient hind-limbs, are represented in 
strata of this age by remains of the ancient ‘“ Sea-Cows,” to 
which the name of Hadlitherium has been applied. Nearly 
allied to the preceding is the likewise aquatic order of the 
Whales and Dolphins (Céefaceans), in which the body is also 
fish-like, the hind-limbs are wanting, the fore-limbs are con- 
verted into powerful “flippers” or swimming-paddles, and 
the terminal extremity of the body is furnished with a 
horizontal tail-fin. Many existing Cetaceans (such as the 
Whalebone Whales) have no true teeth; but others (Dol- 
phins, Porpoises, Sperm Whales) possess simple conical teeth. 
Fig. 228.—Zeuglodon cetoides. A, Molar tooth of the natural size; B, Vertebra, 
reduced in size. From the Middle Eocene of the United States. (After Lyell.) 
In strata of Eocene age, however, we find a singular group 
of Whales, constituting the genus Zeuglodon (fig. 228), in 
